1. Field of the Invention
This invention relates to a method of forming a space portion in a continuous slide fastener chain by removing coupling elements from a predetermined length of section of the slide fastener chain, and more particularly to such a space portion forming method in which coupling elements contiguous to opposite ends of a prospective space portion are precisely positioned without being damaged.
2. Description of the Related Art
Conventionally, in forming a space portion in a slide fastener chain, it was difficult to position a prospective space portion precisely due to various causes, such as errors with individual units, extension and shrinkage of opposite fastener tapes, irregular pitches of coupling elements and inertia when stopping the feed of the slide fastener chain, thus resulting in that the coupling elements contiguous to the opposite ends of the prospective space portion would be damaged or partly cut away. In an attempt to eliminate this conventional problem, various positioning concepts have been proposed to correct the position of coupling elements contiguous to the opposite ends of the prospective space portion. These conventional positioning concepts are exemplified by Japanese Patent Laid-Open Publication No. HEI 3-41904, which discloses a space portion forming method having two positioning devices on the upstream side and the downstream side of a prospective space portion respectively, comprising the steps of positioning the slide fastener chain by actuating a second positioning device downstream of the prospective space portion, cutting off a length of row of coupling elements downstream of the prospective space portion using a punch, then positioning the slide fastener chain by actuating a first positioning device upstream of the prospective space portion, and cutting off a length of row of coupling elements upstream of the prospective space portion.
In the conventional space portion forming method, however, since positioning and cutting must take place twice in forming a single space portion, it would be time-consuming and parts such as a punch would be worn away sooner.